It's made with goose or duck confit, which you can easily make as well. Or use pre-pepared if you like.
To make the confit: You need duck or goose pieces(breast and legs are best), a fair bit of coarse salt, duck fat, sprinkle dried thyme and bay leaf. Put the dry duck pieces in a glass dish, rub all over with the coarse salt(needs to be pretty thickly crusted). Add the herbs, cover and leave in fridge(or a cold pantry) for about 36 hours. After that, melt the duck fat--if you don't have enough, you can add melted pork lard to it too. Take out the duck/goose pieces, drain the liquid, wipe off the salt completely. Heat the fat in a saucepan, cook the meat in it. It needs to simmer for about an hour—if it's properly cooked, the juice will run yellow(test with a skewer.) Cool the meat, put in a jar with the fat on to-it must cover all the meat and a bit more-then cover jar with lid or greaseproof paper. The fat solidifies and preserves the meat. It can be preserved in the fridge or a cold pantry(only in the winter) for a few weeks or used within a day or two if you're in a hurry! You can also make pork or even chicken confit in the same way. But duck and goose are the most traditional.
Pieces of the confit are then used in the cassoulet itself.
For the cassoulet, you need the confit, haricot beans, Toulouse sausage(if none available use Italian sausages)olive oil, onions, garlic, herbs(rosemary, thyme, parsley), tomatoes(fresh or tinned), breadcrumbs, salt, pepper. You can also add some unsmoked bacon(such as pancetta) or pork belly pieces if you like. Proportions depend on how many you're cooking for, but for 6 people you'd need about 500 g beans, 2 garlic cloves, 2 onions, 2 or 3 tomatoes depending on size, ½-2/3 sausage per person, and if using pancetta or pork belly, a little for each person. To prepare the beans, either soak them overnight in cold water, or to do it more quickly, put them in a pan with cold water, without adding salt. Bring this to the boil and cook for 15 minutes. Do not salt the beans until at least half-way through this cooking time(salting them too early makes them harder to cook quickly). Drain the beans. Fry half the onion and garlic in the olive oil, add the beans, pepper, half the herbs, and if you like a little white wine, cover with a little stock or water, simmer till beans are tender. In a different pan fry the rest of onion and garlic, the sausage, pancetta or pork belly, rest of herbs, pepper, a little salt, and tomatoes. When beans are cooked, drain and add sausage mixture to it. Now take out the confit from its jar, heat through in a little of its own fat. Lay it in the bottom of a casserole dish, put the bean/sausage mixture on top. Cover with breadcrumbs, and sprinkle them with olive oil. Cook in oven or under grill till top has gone golden brown.
Serve with salad and a good red wine.